For outside diameters the distance of peaks are 50mm, and for inside measurements it's 52mm. Some calculations are required.
Actually measuring the print will help achieve higher accuracy. The peaks of my print was about 0.4mm off.
For radius measurement CAD is probably the easiest, otherwise some trigonometry will also do. Demo here: https://www.printables.com/model/908014-depth-gauge-to-radius-caliper-adapter
Not designed to be super quick or for easy math, but for compact and versatile design.
Designed for calipers with stem of 16.3mm width and 3mm thickness. Parametric model given.
Print: 0.4mm nozzle, 0.15mm layer height and PETG. No support. Should work with most settings.
Fit for me wasn't perfect, so used some boiling water and slightly dented the backside slightly while soft made it appropriately tight.
The author marked this model as their own original creation.